EGFR and non-small cell lung carcinoma: The results of this meta-analysis comparing the difference in efficacy of EGFR TKI in advanced NSCLC for the EGFR 19del and 21L858R mutations, confirms that the EGFR 19del mutations when treated with EGFR TKI show a better response rate and progression-delaying effect than the EGFR 21L858R mutations.